Method of forming metal parts

ABSTRACT

A method for forming metal parts wherein molten liquid metal is injected into a cavity. The cavity is reduced in size compressing the metal. The cavity is cooled, cooling the metal. The metal is held in the cavity until solidified. The cavity is opened for removal of the formed part. Apparatus for forming metal parts comprises a die housing containing a die with apparatus to connect and separate same and to inject molten liquid metal into the die. The liquid molten metal under pressure is held in the die. Same is cooled simultaneously. An apparatus removes the formed part.

I Unlted States Patent 1 1 1111 3,802,483

Killion et al. [45] A r, 9, 1974 [54] METHOD OF FORMING METAL PARTS 2,867,869 1/1959 Hodler 164/305 x [76] Inventors: Leonard H. Killion, PO. Box 608,

Derby Kans. 67037; E. Blair, Primary ExammerJ Spencer Overholser 9010 women Rd Kansas City Assistant Examiner-John E. Roethel Kans. Attorney, Agent, or Firm-John H. Widdowson [22] Filed: June 7, 1971 57 ABSTRACT [21] App]. N0: 150,467 A method for forming metal parts wherein molten liq- I uid metal is injected into a cavity. The cavity is reduced in size compressing the metal. The cavity is 1 4 6 cooled, coohng the metal. The metal 1s held 1n the [58] Fie'ld 305 313 cavity until solidified. The cavity is opened for re- 1 2 moval of the formed part. Apparatus for forming metal parts comprises a die housing containing a die [56] References Cited with apparatus to connect and separate same and to inject molten liquid metal into the die. The liquid mol- UNITED STATES PATENTS ten metal under pressure is held in. the die. Same is 2 31 11 1 23920 cooled simultaneously. An apparatus removes the u 1ove.... f 1,717,254 6/1929 Polak 164/120 X Ormed part 3,106,002 10/1963 Bauer 164/120 3 Claims, 6 Drawing Figures 92 w J? 92 94 40 M METHOD OF FORMING METAL PARTS Numerous means and methods are well known in the prior art to form metal into parts. Some principal methods of forming metal parts are generally forging, casting and extrusion. Each of these methods has its own peculiar quality which makes it advantageous to use in different situations. However, they all have a substantial and different effect on the grain orientation of the metal formed in each of the processes. The casting method can produce a more uniform grain structure than the other; however, it generally will only produce a part of rough dimensions which must be finished by another process. Forging can produce finished quality parts, but it will reshape the grain structure of the metal slug or piece of metal stock which it uses and this rearrangement can produce undesirable side effects such as decrease in fatigue life. The extrusion process also can substantially alter the grain structure of the stock to such an extent that its final orientation is an undesirable side effect of the process. Primarily the reason for changing the grain structure in these prior art methods is the metal is worked in the solid state, after it has an established grain pattern, and changing its shape then reshapes the grain pattern of course depending on the amount of reshaping done. The means to form the metal parts by these above described methods varies with the methods; however, with the exception of the casting method the metal is pressed or formed when cool or warm and after it has substantially solidified establishing a grain structure pattern.

I In the herein described method and means of this invention a method is provided whereby, liquid molten metal is pressure formed while liquid, simultaneously cooled then removed, and a means is provided to carry out the method. The method and means of this invention provide a way to produce metal parts without the above identified undesirable characteristics and side effects of the prior art.

In a preferred specific embodiment of this invention, a method for forming metal parts includes placing liquid molten metal in a shaped cavity, closing and compressing the cavity, cooling the filled cavity and the metal, then removing the formed metal part when the metal is cool. Also, a preferred specific embodiment of this invention is a means for forming metal parts including a die housing enclosing a die that can be cooled with the die in the compressed and closed position and opened for removal of the formed part. The die and die housing are mountable in a conventional type die press machine and usable with a vacuum ladling system or other die filling systems. The die has removable die face members mounted on cooling block members which in operation shape the metal and cool it.

One object of this invention is to provide a method for forming metal parts overcoming the aforementioned disadvantages of the prior art methods and to provide a means of forming metal parts overcoming the disadvantages of the prior art devices.

Still, one other object of this invention is to provide a method for forming metal parts wherein liquid molten metal is'shaped by compression and cooled to a solid state.

Still, another object of this invention is to provide a method for forming metal parts which produces parts of substantially the finished size and shape which have a uniform grain structure and is not deformed by the shaping process.

Yet, an additional objectof this invention is to provide a means for forming metal parts having a die assembly adapted to receive a shot of liquid molten metal, compress it to conform to the shape of the die face and cool it to a solid state while in compression.

Yet, one further object of this invention is to provide a means for making metal parts that has a coolable die assembly and can be used with conventional die casting machines and conventional molten metal ladling and die filling systems.

Various other objects, advantages, and features of the invention will become apparent to those skilled in the art from the following discussion, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partially cut away perspective view taken from above of a die casting machine having the die of this invention in place;

FIG. 2 is a side elevation view of the die casting machine shown in FIG. 1 having one side thereof removed for clarity;

FIG. 3 is a front elevation view of the die casting machine shown in FIG. 1;

FIG. 4 is a partial cross sectional view of the die assembly with the die in the open position;

FIG. 5 is a partially cross sectional view of the die assembly in the closed position with a part therein; and

FIG. 6 is a partially cross sectional view of the die assembly in the open position with a part held between the separate die portions by the part ejectors.

The following is a discussion and description of preferred specific embodiments of the method and means for forming metal parts of this invention, such being made with reference to the drawings, whereupon the same reference numerals are used to indicate the same or similar parts and/or structure. It is to be understood that such discussion and description is not to unduly limit the scope of the invention.

Referring to the drawings in detail and in particular to FIG. 1 showing a conventional type die casting ma-. chine, indicated at 10, and adapted to accommodate the means for forming metal parts of this invention. The means for forming metal parts in a preferred specific embodiment of this invention is a die assembly 14 including a die housing 16 with an internal die assembly 18 and having cavities in the die housing 16 used to heat and cool the die assembly 14.

The die casting machine 10 has jaws forming a clamp to hold the die assemblyl4 that are hydraulically operable to open and close the major portions of the die housing 16. The die casting machine 10 has an upper hydraulic cylinder 20 and a lower hydraulic cylinder 22 which are adapted to operate the internal die assembly 18. The die casting machine 10 is operated by a pump and reservoir, indicated at 24 and controlled by a separate control system, not shown. Additionally, the die casting machine 10 is equipped to heat and coolthe die assembly 14 as will be described. The die casting machine 10 and other apparatus of the herein described invention is described as being used with a vacuum ladling system to fill the die; however, it is to be understood that it is not to limit the use of the invention to that die filling system alone.

The die housing 16 is shown in detail in FIGS. 4, and 6. As can be seen, it has two separate outer members 28 and 30 that enclose the internal die assembly 18. The outer housing members 28 and 30 are mounted with the opposing jaws 32 and 34 of the die casting machine so they can be opened and closed as necessary. The die assembly 14 as shown in FIG. 1 is enclosed in a protective and thermally insulative jacket 35 and thus does not have the same outward appearance as the die assembly 14 shown in the other figures. Inside the die housing 16 the internal die assembly 18 moves in an elongated cavity between the outer housing members 28 and 30. The internal die assembly 18 includes a pair of opposing pistons 36 and 38 which extend from the outer ends of the die housing members 28 and 30, respectively, and are movable by the hydraulic cylinders of the die casting machine 10. The pistons 36 and 38 are preferably sealed with the cavity by O-rings 40, as shown, and are threadedly attached to die block members 42 and 44. It is to be noted that the pistons 36 and 38 can be sealed by means other than O-rings, so long as the die cavity is sealed closably. The die block members 42 and 44 are smaller than the inner ends of the pistons 36 and 38 and extend coaxially from them. The innermost surfaces of the die blocks 42 and 44 are the faces of the die. These die faces 46 and 48 are the surfaces against which the liquid molten metal is pressed when in operation. The die face members 46 and 48 are shaped to the actual size and shape of the desired part for reasons to be explained in the hereinafter. Part ejector members 54 and 56 extend through the plungers, die blocks and die faces. One part ejector 54 extends through plunger 36, die block 42 and die face 46; and the other part ejector 56 extends through the plunger 38, die block 44 and the die face 48. Both part ejectors 54 and 56 extend so as to be flush with the die faces 46 and 48 for the forming operations then extend past them to remove the formed part as indicated in FIG. 6. A sleeve member 58 surrounds the matching ends of the die block members 42 and 44 and has apertures for access to the shot receiving cavity 60.

The opposite end members 28 and 30 of the die housing 16 have apertures 62 and 64, respectively, that connectthe portion of the cavity behind the pistons 36 and 38 to the outside of the housing. Additional apertures 66 and 68 through the enlarged portion of the pistons 36 and 38 provide access from the cavity behind the pistons to the cavities 37 and 39 inside the die blocks 42 and 44. These passageways are used to transfer fluid to heat and cool the die assembly 18; they are connected to conduits 70 on the outside of the die housing 16. The conduits 70 are attached to one side of the die assembly 14 and connect it to a separate heat source. The lower conduit 72 is preferably flexible so that the lower portion of the die assembly 18 can be lowered for opening the die housing for operation.

The center portion of the die housing 16 has two apertures therethrough its opposite sides with the apertures being partially formed partially in the segments of the housing. The inlet aperture 74 is adapted to receive the molten metal and pass it through a tapered aperture 76 in the sleeve member 58. The inlet aperture 74 is connectible to a molten metal conduit 78- which in operation supplies molten metal to the die assembly. The other apertures 80 is adapted to be connected to a vacuum source. The vacuum aperture 80 is connected to a passageway 82 in the sleeve member 58. A vacuum source is connected to the aperture by a conduit 84.

It is to be noted the inner end of the passageway 82 is at one of the highest points in the shot cavity 60; this is necessary in order to evacuate air that may become trapped in the cavity 60 as the molten metal comes into it. With the die assembly 14 as shown in the figures, it fits into the die casting machine 10 with the die housing 16 vertically and the outer housing member 30 on top. This vertical orientation of the die assembly 14 will place the innermost end of the vacuum aperture 82 at a highest point in the shot cavity 60.

The center portion of the die housing 16 has a series of passageways from the outside to the die block cavities 37 and 39 that are used to transfer heating fluid from the cavities. The upper housing member 30 has a passageway 86 therethrough adjacent to the vacuum aperture 80 connecting to an aperture 88 in the sleeve member 58 and connecting to the passageway 90 in the die block 44. The lower housing member 28 has a passageway 92 therethrough adjacent to the vacuum aperture 80 connecting to an aperture 94 in the sleeve member 58 that connects to the passageway 96 in the die block member 42. The passageways 86 and 92 are attached to a conduit 98 extending from the side of the die assembly 14. One additional aperture 98 in the center portion of the die housing 16 is provided spaced above the vacuum aperture 80. The aperture 98 is provided in the housing member 30 as a place for a thermocouple to be mounted; it is positioned sufficiently near the shot cavity 60 to provide a place to measure the temperature of the internal die assembly 18.

In brief, the operation of the die assembly 14 in the die casting machine 10 is as follows: The die housing 16 is in the position shown in FIG. 4 and the internal die assembly 18 is heated by steam or the like passing through the cavities 100 and 102 behing the pistons 36 and 38, through passageways 66 and 68 into the cavities 37 and 39 of the die blocks 42 and 44 and exiting through the passageways 96, 94 and 92, and 90, 88 and 96. It is to be noted the internal die assembly 18 can be heated by other means than steam heat, such as electrical resistance or induction through the die housing 16. With the shot cavity 60 open a precise quantity of moltenmetal is injected into it through the tapered aperture 76. The shot cavity 60 is evacuated by the vacuum source having access to it by the passageway 82; this removes any air which may be trapped in the cavity 60. The passage of steam through the internal die assembly 18 can be increased by raising the flow to the inlets 62 and 64; this causes pressure to build up in the cavities 100 and 102 behind the pistons 36 and 38 and they move inward to exert a forging pressure to form the metal part. The forging pressure is held on the part for a period of time until it is cooled sufficiently to be removed from the die assembly 18. While the forging pressure is applied, the die assembly 14 is in the position shown in FIG. 5 with the part shown in double crossed lines. The formed part 110 is cooled by the steam flowing through the internal die assembly 18. It is to be noted the temperature of the internal die as sembly 18 can be controlled by the temperature of the fluid flowing through it; also, the fluid need not be steam; it can be any fluid that can be supplied in a sufficient quantity to maintain the forging pressure on the part 110. Forging pressure is accomplished by fluid pressure behind the pistons and force exerted on the pistons from outside the die housing 16 transmitted through the attached sleeve shown around the part ejectors 54 and 56. For instance, if the part 110 is desired to be cooled quickly then steam could be used to heat the internal die assembly 18 then a cryogenic fluid such as liquid oxygen could be introduced to rapidly chill the die 18. Or if a less extreme cooling effect is desired, cooler steam, freon or other gaseous fluids or other liquids could be used.

When the part 110 is cooled sufficiently to be removed or to the desired temperature, the die housing 16 is opened by the die casting machine and the housing members 28 and 30 are separated as shown in FIG. 6. The part ejectors 54 and 56 press the part 110 from the die faces 46 and 48. Once the part 110 is removed from the internal die assembly, the part ejectors 54 and 56 can be retracted releasing the part 110 for removal.

In reference to the method for forming metal parts of this invention, it is easily described in conjunction with the above described means for forming metal parts. However, it is to be understood that the herein described method for forming'metal parts is not to be restricted by the herein described means for forming metal parts. It is to be further understood the method for forming metal parts of this invention can be accomplished by means other than the herein described means for forming metal parts.

The method for forming metal parts of this invention necessarily requires the use of a die apparatus constructed with the specific structural components necessary to accomplish it. The die assembly 14 as described supra has all the necessary structural features to carry out the method for forming metal parts of this invention and for purposes of illustration will be used in description of the method. The die assembly 14 has a shot cavity 60 in which molten metal can be placed, die faces 46 and 48 to shape the molten metal, pistons 36 and 38 which are used to exert forging pressure on the molten metal, a plurality of passageways and cavities usable to pass fluid to heat and cool the die assembly andother elements. The die assembly 14 is preferably operated by a die press machine 10 which has the fea ture of performing the forming operation consistently and repeatedly. I

The method of forming metal parts of this invention initially requires the die assembly to be generally in the position shown in F IG. 1 with no material in the forging cavity 60. The die assembly is heated by high temperature fluid being circulated through it. The fluid passes into the die housing through the apertures 62 and 64, through the apertures 66 and 68 in the pistons 36 and 38, through the cavities 37 and 39 in the die blocks 42 and 44 and passes from the die assembly by connected passageways 96, 94, 92 and 90, 88, 86. When the die assembly 14 has reached an appropriate predetermined temperature, a quantity of molten metal is ladled into the cavity through the apertures 74 and 76. The quantity of molten metal is equal to the volume of the part which is to be formed plus an amount to allow for shrinkage so the volume when the metal is cool is the volume of the desired part. The amount a specific materal will shrink depends on the material itself and the temperature range involved. A vacuum system is used to ladle the molten metal into the forging cavity 60; it is basically a vacuum acting on one side of the forging chamber through an aperture 82 which removes entrapped air in the cavity and pulls the molten metal into the forging cavity 60. The use of vacuum ladling sys' tems such as this one have been found in practice to be highly desirable because of the trapped air removal feature. Other die filling systems which are also highly desirable use a combination of vacuum on one side of the die and molten metal under pressure on the other side to fill the die.

When the specific quantity of molten metal has been introduced into the forging cavity 60, the cavity is reduced in size to exert the forging pressure on the molten metal. Also, simultaneously the temperature of the die assembly is reduced which cools the molten metal. In the die assembly 14 the flow of fluid is increased a substantial amount; this builds up pressure behind the pistons 36 and 38 urging them toward each other, the die faces 46 and 48 press into the molten metal and it forms around them. Forging pressure exerted on the metal is created by the fluid pressure build up behind the pistons 36 and 38 and the forging pressure can be varied by varying the amount of fluid flowing through the pistons and die blocks. The flowing fluid is used to cool the die assembly 14. Changing the temperature of the fluid from a high temperature to a lower temperature will change the temperature of the die assembly. For instance, steam can be used as the cooling fluid, particularly high temperature steam can be used to heat the die assembly and lower temperature steam can be used to lower the temperature of the die assembly. The temperature range desired to be controlled is necessarily dependent on the specific metal to be formed. It should be noted there are other fluids than steam which can be used to control the temperature of the die assembly 14. For instance, where rapid and extreme chilling of the die assembly is desired, steam could be used to heat it and a cryogenic fluid such as liquid oxygen could be used to cool it.

Once the die assembly 14 is cooled to the desired temperature, it is held at that temperature and the forging pressure is maintained until the metal has solidified sufficiently to be removed from the die assembly 14. The position of the die assembly 14 when exerting the forging pressure on the metal is shown in FIG. 5. The formed metal part is indicated at and shown in the cross-hatched lines.

When the metal part 110 is sufficiently solidified to be removed from the die assembly 14, the fluid flow is stopped to relieve the forging pressure. The die press machine 10 then opens the die housing 16, retracts the pistons 36 and 38 and the sleeve member 58. Because the metal part 110 has been pressed around the die faces 46 and 48, it will usually adhere to one or the other. In order to remove the formed part 110 from the die faces, part ejectors 54 and 56 are provided to extend from the die blocks 42 and 44 and press the formed part 110 from the die faces. When open for removal of the formed part, the die assembly 14 is in the position shown in FIG. 6; The part 110 is pressed from the die faces and held between the separated portions of the die assembly by the part ejectors 54 and 56. Once the part 110 is removed from the die faces, the part ejectors can be retracted and the part removed by hand or other means.

In the use of the method for forming metal parts of this invention, it is seen that same provides a method by which metal parts can be formed to their precise finished size and shape. The method of this invention provides a method of forming metal parts which produces parts that do not have the heretofore stress concentrations and disturbed grain structures of prior art forgings; it produces metal parts with a more uniform grain structure and less stress concentrations due to forging. The method of forming metal parts of this invention can be practiced with a conventional type die press machine and molten metal ladling system utilizing a specially constructed die assembly.

In the manufacture of the means for forming metal parts of this invention, it is obvious the die assembly 14 and die housing 16 can be constructed of typical die materials and by typical die making processes. The die assembly 14 can be constructed of sufficient size and strength to be used with commonly forged materials and accommodated in conventional die press machines 10.

in the use and operation of the means for forming metal parts of this invention, it is seen the die assembly 14 can be used with conventional die press machines and vacuum ladling systems and only requires a separate fluid system for heating and cooling the die. The means of forming metal parts can be used in continuous pouring type operations where a die assembly is used to repeatedly form metal parts in a manufacturing type environment.

As will be apparent from the foregoing description of the applicants method and means for forming metal parts, relatively simple method and means have been provided to form metal parts. The method and means accomplish the forming of metal parts which are adaptable to manufacturing processes and existing type manufacturing machines.

While the invention has been described in conjunction with preferred specific embodiments thereof, it will be understood that this description is intended to illustrate and not to limit the scope of the invention, which is defined by the following claims.

I claim:

1. A method of forming metal parts comprising:

A. ladling molten metal into a forging cavity,

B. exerting forging pressure on the molten metal in the forging cavity,

C. reducing the temperature of the forging cavity, thereby cooling the molten metal simultaneously with said exertion of forging pressure,

D. the forging cavity is cooled by cooling fluid passing adjacent to same,

E. said exertion of forging pressure of the forging cavity is accomplished by pressure of the cooling fluid on the forging cavity,

F. holding the molten metal in the forging cavity until solidified, and

G. opening the forging cavity to provide for removal of the solidified metal part.

2. The method of forming metal parts as described in claim 1, wherein:

a. ladling a quantity of molten metal into the forging cavity which is a volume greater than the volume of the desired part by an amount sufficient to allow for shrinkage of the metal to the desired volume,

b. said exertion of forging pressure on the forging cavity is sufficient to cause the molten metal to conform to the shape of the forging cavity,

c. said reduction of the temperature of said forging cavity is sufficient to quickly cool the molten metal to a solid state, and

d. said opening of the forging cavity is done when the metal is in a solid state.

3. The method of forming metal parts as described in claim 2, wherein:

a. the forging cavity has the shape and size of the desired part,

b. the forging cavity is pre-heated to a temperature slightly below the temperature of the molten metal, and

c. the forging cavity is cooled to a temperature greatly below the temperature of the molten metal. 

1. A method of forming metal parts comprising: A. ladling molten metal into a forging cavity, B. exerting forging pressure on the molten metal iN the forging cavity, C. reducing the temperature of the forging cavity, thereby cooling the molten metal simultaneously with said exertion of forging pressure, D. the forging cavity is cooled by cooling fluid passing adjacent to same, E. said exertion of forging pressure of the forging cavity is accomplished by pressure of the cooling fluid on the forging cavity, F. holding the molten metal in the forging cavity until solidified, and G. opening the forging cavity to provide for removal of the solidified metal part.
 2. The method of forming metal parts as described in claim 1, wherein: a. ladling a quantity of molten metal into the forging cavity which is a volume greater than the volume of the desired part by an amount sufficient to allow for shrinkage of the metal to the desired volume, b. said exertion of forging pressure on the forging cavity is sufficient to cause the molten metal to conform to the shape of the forging cavity, c. said reduction of the temperature of said forging cavity is sufficient to quickly cool the molten metal to a solid state, and d. said opening of the forging cavity is done when the metal is in a solid state.
 3. The method of forming metal parts as described in claim 2, wherein: a. the forging cavity has the shape and size of the desired part, b. the forging cavity is pre-heated to a temperature slightly below the temperature of the molten metal, and c. the forging cavity is cooled to a temperature greatly below the temperature of the molten metal. 